The present invention relates to fabrics, yarns and processes for making yarns. In particular, the present invention relates to yarns having an internal core of a glass material encased in an outer fiber, and a process of spinning fibers about a glass material core to form yarns having enhanced strength and cut resistance.
It has been known in the textile field to blend or process para-aramid fibers or filaments with other fibers to produce yarns of cut fibers that have enhanced strength and cut and heat resistant properties, for use in forming fabrics or materials for forming protective garments such as cut resistant gloves, etc. Typically, such fibers are spun into yarns using open-end, ring or friction spinning machines that spin the fibers together to form a yarn, or through the use of an industry standard ring twister or a two-for-one twister, wherein each filament is wrapped around each other to produce a single strand of yarn, with each strand being at least partially exposed to the exterior of the total strand. It is further known in the textile field that glass or fiberglass filaments or fibers provide enhanced cut resistance and strength and, therefore, it has been known to use such fibers in conjunction with para-aramid or other fibers to form enhanced cut and heat resistant yarns.
Glass and fiberglass filaments are inherently very hard and smooth, but tend to be very brittle. This brittleness makes it difficult and somewhat impractical to knit yarns of cotton and/or para-aramid fibers with glass or fiberglass filaments, unless some type of protective sheath yarns is twisted or cabled about the fiberglass/glass filaments. For example, U.S. Pat. No. 5,845,476 describes a process of cable twisting filaments wherein different filaments or yarns are wrapped around a core bundle of fiberglass fibers with the outer wrap thus serving as a cover or protective sheath for protecting an inner fiberglass core. This cover protects the fiberglass core from breaking easily during a knitting process and produces a relatively stable yarn, since the fiberglass core is generally substantially covered.
The problem with cable twisting sheath yarns about an inner fiberglass or glass core is that, typically, this process is somewhat slower than conventional yarn spinning processes and is fairly expensive, since the outer yarns must be very tightly wound about the core yarns in order to substantially cover and protect the core yarns from exposure. However, while more conventional yarn spinning processes generally are cheaper and easier, the inherent smoothness of fiberglass and glass filaments tends to allow para-aramid and other fibers to slide or slip off of the smooth, slick core glass filaments. If the mass ratio of the wrapper or sheath fibers to the mass of the core fibers is too low to insure the proper covering of the core, the core will tend to show through the finished yarn and the outer-wrap will tend to slide easily on the core. As a result, slippage occurs during which the wrap or sheath yarns slide and bunch along the filament, thereby exposing the entire core yarn and leading to yarn breakage or weaving machine failure due to resistance of the bunched fibers.
Further, during knitting processes, the core yarns may become exposed to knitting needles that can bend and slide the yarn at excess angles, and thus can engage the glass or fiberglass filaments and cause the breaking thereof. As a result, when such glass core yarns are used in making fabrics for woven clothing, the fabrics typically have broken ends of glass fiber protruding through the outer wrapping or sheath fibers. Such protruding broken fibers can irritate the skin of a wearer and leave the fabric with a rough, unsightly finish and appearance.
Proposed solutions to this problem include processes such as disclosed in U.S. Pat. No. 4,384,449, which discloses the assembling or forming of a yarn having a core made from an inorganic glass with aramid fibers or filaments wound thereabout in counter-directional helixes, such as shown in FIG. 1. This winding addresses the problems of sheath slippage in knitting by providing a cable twisting type process. However, this process uses filaments or pre-formed spun yarns, and, because cabling processes are generally slow, the cost of such yarns typically is fairly high. Similarly, U.S. Pat. No. 5,035,111, proposes minimizing slippage of a sheath yarn from about a core by introducing a yarn with a higher coefficient of friction, to be used as part of the core yarn, along side or in parallel with a yarn having a lower coefficient of friction. Such a dual filament core ultimately increases the cost of the finished yarn product, and in many cases, creates a yarn of a larger size than is needed or desired. In addition, exposure and breaking or splintering of the lower coefficient of friction inorganic filaments can still occur. As stated, such splintering or breaking of the glass fibers tends to result in the glass fibers protruding through the outer sheath yarns and contacting the skin of a person wearing the fabric made from such yarns, thereby causing unacceptable irritation to the wearer and providing a less than finished appearance to the fabric.
It therefore can be seen that the need exists for a process of forming a yarn having a glass or fiberglass core to impart enhanced properties to the yarn, while both allowing for the yarn to be made inexpensively and minimizing the chance of splintering or breaking of the glass core during subsequent knitting and/or weaving operations.
The present invention includes, among other aspects, a yarn having a roughened core and methods of making such yarns. A yarn is provided having a core formed of a glass material, wherein at least a portion of a surface of the core is roughened. The core may be a glass filament or a filament including a glass material. A fiber is applied to the core. The fiber may be in the form of a wrapping yarn wound about the core. The fiber or wrapping yarn may substantially cover the core, in order to prevent exposure of the core and possible damage thereto. The fiber may include at least one polymer selected from aramids, para-aramids, polyesters, polypropylenes, nylons, cellulosics and co-polymers and blends thereof, as well as other polymers and materials. A yarn having such a core and fiber combination may display, along with other properties, excellent cut resistance, strength and heat resistance. Fabrics, garments and other articles formed of such yarn may also display such properties and are other aspects of the instant invention.
A method of making a yarn with such a roughened core generally will include roughening a surface of the glass-containing core and applying a fiber thereto. The fiber applied thereto may be in the form of a wrapping yarn wound about the core. This wound wrapping yarn may substantially cover the core. The method of making the yarn may include mechanical and/or chemical roughening of the glass core. Mechanical roughening of the core may include contacting a glass, fiberglass or similar high strength, cut resistant fiber or filament, intended to form the core, with a roughening mechanism or assembly. Such a roughening assembly could include, for example, a series of one or more rollers having glass filaments wound thereabout or guide tubes or similar mechanisms having an abrasive material applied over their surfaces and about which the core glass filament is passed.
These and other features, objects, and advantages of the present invention will become more apparent upon review of the detailed description set forth below when taken in conjunction with the accompanying drawing figures, which are briefly described as follows.